<!DOCTYPE html>
<p>Test that an empty spanner B between spanners A and C prevents margins on A and C from collapsing.</p>
<p>There should be a blue square below.</p>
<div style="-webkit-columns:3; width:10em; background:blue;">
    <div id="a" style="-webkit-column-span:all; margin-bottom:5em; background:white;"></div>
    <div id="b" style="-webkit-column-span:all;"></div>
    <div id="c" style="-webkit-column-span:all; margin-top:5em; background:white;"></div>
</div>
